Technical Field
The present disclosure relates to compositions and methods in the onshore and marine (offshore) hydrocarbon exploration, production, drilling, well completion, well intervention, and leak containment fields.
Background Art
While the present discussion centers on additives for drilling fluids, it will be recognized that the fluids discussed herein are not so limited in their use. Drilling fluids have been used for decades in the hydrocarbon recovery field and other fields. The two basic types known in the art are water-in-oil (W/O) emulsions or dispersions, which are also referred to herein as oil-based drilling fluids, oil-based muds, or oil-based mud systems; and oil-in-water (O/W) emulsions or dispersions, which are also referred to herein as water-based drilling fluids, water-based muds, or water-based mud systems. In W/O drilling fluids, a minor amount (<50%) of an aqueous phase is dispersed in a major amount (>50%) of an hydrocarbon phase. In O/W drilling fluids, a minor amount (<50%) of an oil or hydrocarbon phase is dispersed in an aqueous phase. The present disclosure is concerned with additives for O/W drilling fluids, the resulting drilling fluids, and methods of using same in drilling and other operations.
When drilling in or through shale rock to reach or explore for a hydrocarbon-bearing subterranean formation, the industry has encountered challenges, which have become more acute in light of recent developments in so-called unconventional shale oil and gas recovery. Problems for the drilling fluid additive formulator, when the fluid is to be used for drilling in or through shale to reach a hydrocarbon-bearing subterranean formation include: finding the right components to provide desired effects (lubricity, shale inhibition, ROP (rate of penetration), and wellbore stability; ensuring HSE compliance (toxicity, safety (corrosivity, flash point, non-oxidizing), and environmentally acceptable); combining the components in such a manner that they have long-term stability, the right viscosity, and reasonable pour point; ensuring the fluid does not negatively impact properties of both clay and polymer-based drilling fluids, especially viscosity and API Filtrate; and finding components heat stable to 300° F. (149° C.). The drilling fluid additives of the present disclosure seek to enhance the performance of water-based drilling fluids in terms of one or more of lubricity, shale inhibition, ROP, and/or wellbore stability.
Certain drilling fluid additives are known in the art. U.S. Pat. No. 4,988,450 discloses additive compositions and aqueous drilling fluids which impart improved wellbore stability in drilling shale formations consisting essentially of one or more water-soluble high molecular weight polymers capable of forming relatively strong nucleophilic sites when treated with base and one or more potassium salts which have sufficient alkalinity to raise the pH of the resultant drilling fluid to above 9.0, but whose anions are relatively weak nucleophiles compared to the polymeric nucleophilic sites. While wellbore stability may be improved, there is no discussion of lubricity, or additive ingredients that may improve this property. Several drilling fluid additive patents disclose the use of lecithin. U.S. Pat. Nos. 6,462,096 and 8,389,447 disclose oil-based drilling fluids containing certain organoclays as rheological additives for use in high temperature drilling applications, and lecithin as one of the preferred surfactants or emulsifiers. U.S. Pat. No. 7,008,907 discloses oil-based drilling fluids containing as a first part a carboxylic acid-terminated polyamide and/or a wetting agent, and as a second part a mixture produced by the Diels-Alder reaction of dienophiles, preferably carboxylic acids, polycarboxylic acids, acid anhydrides, or combinations or mixes thereof, with a mixture of fatty acids and resin acids. These two components or parts are blended or mixed and further reacted with cations to form soaps. Lecithin is one preferred wetting agent. Both patents relate to oil-based drilling fluids. U.S. Pat. No. 8,193,125 discloses oil-in-water and water-in-oil drilling fluids, and in the case of water-in-oil emulsions, suitable emulsifier components are alkyl(poly)glycosides of long-chain alcohols and also the fatty alcohols of natural and/or synthetic origin or alkylolamides, amine oxides and lecithins. The '125 patent mentions that use of alkyl(poly)glycoside compounds (APG compounds) as emulsifiers may be of particular interest because of their ecological compatibility. U.S. Pat. No. 8,236,735 discloses oligoglycerol fatty acid ester lubricant additives for drilling fluids, wherein the drilling fluid to which the additive may be added may include fatty alcohols of natural and/or synthetic origin or alkylolamides, amine oxides and lecithins. U.S. Pat. No. 7,268,100 discloses an a water-based drilling fluid comprising a choline salt or a plurality of choline salts given by the general formula: HOCH2CH2N+(CH3)3.R1COO−, wherein R1 is an alkyl group, alkenyl group, alkynyl group, an aryl group, an alkaryl group, an aralkyl group, alkenylaryl group, aralkenyl group, alkynylaryl group, aralkynyl group hetero atom analogs, where the hetero atom is selected from the group consisting of boron, nitrogen, oxygen, fluorine, phosphorus, sulfur, chlorine, bromine, iodine, and mixture or combinations thereof, or mixtures or combinations thereof, a foamer, and water. U.S. Pat. No. 7,786,049 discloses drilling fluids with improved shale inhibition and methods of drilling in subterranean formations. In our recent paper, “Utilizing the Unique Properties of Multi-Hydroxyl Alcohols to Drill Reactive Shales while Maintaining Environmental Compliance”, AADE-13-FTCE-19, presented at the February, 2013 American Association of Drilling Engineers (AADE) National Technical Conference and Exhibition, we disclosed a water-based drilling fluid additive based on multi-hydroxyl alcohols. An optimized system was disclosed as a formulation consisting of a balance of polymers, water loss reagents, vegetable oil lubricant known under the trade designation L-20 (ViChem Specialty Products LLC, Conroe, Tex., USA), multi-hydroxyl alcohol (MHA) Base Fluid, and shale inhibitor known under the trade designation SI-60 (ViChem) optimized by testing to deliver optimal shale inhibition for each of several shale samples. Each of the aqueous drilling fluids was pH adjusted to 9.0.
Despite these improvements, there remains a need for additive formulations for water-based drilling fluids comprising the right components to provide desired lubricity, shale inhibition, ROP, and wellbore stability, while ensuring HSE compliance, long-term stability, viscosity, and reasonable pour point. There also remain a need for additive formulations that do not negatively impact properties of both clay and polymer-based drilling fluids, especially viscosity and API Filtrate, and finding components heat stable to 300° F. (149° C.). The compositions and methods of the present disclosure are directed to these needs.